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Watertight Enclosure Intro and Questions


(Rusty) #1

Hello everyone!

We launched our 2"-Series and 4"-Series watertight enclosures today and I want to start a discussion topic for any questions or comments that might arise.

Check out the blog post here: https://www.bluerobotics.com/new-product-watertight-enclosures/

2"-Series Documentation page: http://docs.bluerobotics.com/watertight-enclosures/2-series/
And the 2"-Series store page: https://www.bluerobotics.com/product-category/watertight-enclosures/2-series/

4"-Series Documentation page: http://docs.bluerobotics.com/watertight-enclosures/4-series/
And the 4"-Series store page: https://www.bluerobotics.com/product-category/watertight-enclosures/4-series/

Feel free to ask any questions you might have!

-Rusty


(Harold Scadden) #2

Congrats on the product release …

Thought I would ask a few questions. While looking through the documentation I didn’t see any information for the screws in the event that you loose one during assembly etc. What is the recommended type of screw that you would use for securing the new end caps with?

Also, is there any requirement to put dressing on the threads to prevent sticking or anything like that? Just curious if you recommend anything to alleviate possible corrosion on the threaded areas or perhaps some sort of fresh water flush post operation. I am asking about that because some of my diver friends talk about washing down their tanks / gear after a saltwater dive with Aluminum tanks.

 


(Andrew) #3

Having just received a 4’'enclosure I have to say I am impressed by what I got and the price. I am now looking at the 2" enclosure it could be ideal for making lights. Can’t wait to complete my project


(Rusty) #4

Harold,

Good point. We’ll add info on the screws to the documentation. They are M3x16 for the 12mm end-cap on the 4"-Series and M2x10 for the 6mm end-cap on the 2"-Series. The screws are Stainless Steel 316 to minimize corrosion.

For long-term exposure to seawater it would be a good idea to dip the screw threads in silicon grease to protect against sticking. It’s definitely a good idea to rinse the enclosure in fresh water as well.

Andrew,

Thanks for the feedback!

-Rusty


(Paul) #5

The housings look great! I’m looking at the drawings and have two questions: What are the tabs on sides of the end caps for? Is there a provision in the design to physically hold the end caps to keep them from “popping” off?


(Harold Scadden) #6

Paul I did design the caps, but from messing with seal systems like this … the tabs are more than likely to allow you to remove the caps without screaming to much!

As for the end caps popping off, the pressure as you go down will keep the caps on.

From the design, you will see the “enclosure vent”. This plug, without the sealing part installed, will allow pressure within the water tight enclosure to “vent” out while you are putting the end caps on. Once you have installed the end caps, you plug up the vent port and the caps should remain in place.

Since there is a double o-ring race in the caps, you end up forming a vacuum seal between those o-rings when you install the caps and that is why I speculate the “tabs” on the side are there to help you pull off the end caps. When you do wish to pull off an end cap, I would highly suggest that you open the vent plug or you are going to have a fun time doing it.

I think there should be a “dis-assembly” procedure along with the existing instructions. What I said above about the vent plug etc. is going to be true. If you install the caps and say it is like 75 degrees in your house or a really hot day out on the boat where you are getting ready to send your ROV on its voyage … once it gets in the water the temperature WILL drop inside of the enclosure and it will create a vacuum. I can imagine some poor guy ranting and raving about the caps don’t come off … what the heck!!!

The vent plug should be open whenever you are putting the caps on and removing them.

Just a suggestion.


(Rusty) #7

Harold is exactly right about the tabs. They help when it comes time to remove the flange from the tube. I’ll add that to the product description and docs for future reference.

There are no retaining rods as the flanges are designed to stay in place with friction as well as water pressure, once submerged. That said, since the end-caps are laser cut it would be fairly easy to make end caps with larger tabs and holes for retaining rods. If enough people are interested we could add that to the store.

Harold, good suggestion on the “disassembly” procedure. We’ll add that to the documentation.

-Rusty


(Joe) #8

Hello Everyone

I just recently discovered your site and therefore am new.

I am looking at your 4" closure to built my second ROV but am thinking I want to have a dome for the pan and tilt of the camera, and was wondering if this is something you have been exploring or is in the works.

I was thinking my next hull was going to be 5" but your 4" kit with the end caps would save me a lot of work on sealing, if you have a longer length, I don’t suppose you are offering a 5" hull

Anyway looks like some great products

Joe

 

 

 


(Rusty) #9

Hi Joe,

Welcome! We’ll have a dome end-cap in the relatively near future, so please keep an eye out for it. If you want to get started, the dome will be an upgradeable option that you can add later.

We are not planning to have 5" size soon, unfortunately. We do offer custom lengths of the 4" enclosure.

-Rusty


(Manolis) #10

Hello everybody !

What about the heat generated by the esc’s and the lighting leds ? Will the air inside the pressure vessel expand so to pop the end cups out, or at least deform the enclosure itself and compromise the watertightness of the pressure vessel? We are talking about a maximum of six esc’s and a few 3w cree leds plus a rpi2, modified power plug and and an apm in such a confined space.


(Rusty) #11

Hi Manolis,

We spent a lot of time thinking about this when we designed the enclosure. The pressure increase with temperature is actually relatively minor.

For instance, say the surface temperature is 25C or around 300K. You close things up and go in the water. As you are driving the ROV with lights, ESCs, etc., the inside heats up to 50C or 325K. That creates a increase in pressure of:

P2/P1 = T2/T1 = 325/300 = 1.083 = 8.3% increase in pressure

That’s the same increase in pressure experienced at a depth of 0.83m, meaning that at 0.83m and less there would be a small force pushing the caps outward. Fortunately, there is friction from the O-rings against the tube. Considering the area of each end-cap and the internal pressure increase, the force on each end-cap would be only 0.1 lb (0.045 kgf), which is not enough to overcome friction in our experience. That force will quickly decrease if the end-cap actually moves.

Note that this is for empty enclosures. Once you put stuff inside, the pressure increase will be less dramatic. This is also using ideal gas laws, which are not perfectly accurate but good enough for an estimate here.

Overall, this could be an issue for extreme situations with very high heating, but otherwise the effect is negligible.

I hope that answers your concerns!

Best,

Rusty


(Pierre Vella-Zarb) #12

Hello everyone,

I finally got around to building my BlueROV with T200 thrusters and blueESC’s and have a problem with the cap I was sent which only comes with 10 holes. I need at least 14, but likely 16 to be safe unless I am thinking this wrong. I need 6 for the thruster cables, 6 for the blueESCs one for vent, one for control and two minimum gor power or other.

Is there an end cap with more holes, ideally made specifically for my BlueROV configuration which looks like the current one in the store? And does it come with the penetrator nuts and bolts?

I’m stuck in my build now! :frowning:

Pierre


(Rusty) #13

Hi Pierre,

Sorry you’re stuck! A few things:

  1. You can actually install both BlueESC wires into a single penetrator. We have a number of people do this with success. I would recommend doing this so that you have as many penetrators as possible for expansion.

  2. We will have a 14 hole end-cap available in approximately 4-6 weeks.

Best,

Rusty


(Pierre Vella-Zarb) #14

Hi Rusty,

To put both the power and control into one penetrator, you would have to pot both sides if I understand you correctly.

Alternatively, I could go with a separate power enclosure or possibly rewire the power lines into the thrusters to put them all in parallel and then have only one power cable into the enclosure. That may result in reduced voltage to the last thruster in line.

Other alternative is an external potted power bar which would be messy to reconfigure if needed.

Has anyone tried one of these options with the BlueESC + T200?

Thank you,

Pierre


(Rusty) #15

Pierre,

What do you mean by “pot both sides” for the penetrator with both cables? You normally pot the penetrator from both ends to ensure that it is sealed well.

The power bar is also an option but it is definitely messy to reconfigure if needed.

Best,

Rusty


(Pierre Vella-Zarb) #16

Hi Rusty,

I now see that the penetrator should be potted from both sides. That makes more sense now.

So I will need to decide if I am going with a separate battery enclosure or double up the cables. Both seem good. Need to consider the dive time and batteries to make the decision.

Thank you for the direction.

Pierre


(TCIII) #17

@Pierre,

I have six of the T100 BlueESC Thrusters and am employing a two WTC ROV configuration.

I have six BlueESC power cables entering the Battery Compartment WTC and six BlueESC control cables entering the Navigation Controller WTC.

Example:


Regards,

TCIII AVD